Actually, that is not just an issue for the future. There are several examples from the past of enviromental cures that have turned out to be worse than the original problem. One of the biggest, and perhaps the best known, is the story of the introduction of Cane Toads to Australia.

Originary of South America, and imported to Australia in 1935 as a scientific way to control beetles that were destroying sugarcane crops, cane toads are still spreading to this day. They are harming native wildlife, poison household pets, and are unstoppably expanding their range at up to 50 kilometers (30mi) per year.

And of course the cane toads have failed to do anything to the beetles.

There is no need to repeat such a mistake on an even larger scale, by depositing sulphur in the upper atmosphere or dumping iron in the open oceans. It is high time we admit that natural systems are way beyond our control and our best bet is adaptation and the use of simple, clear technology.